1. Field of the Invention
This invention relates to a two stroke cycle rotary internal combustion engine, and in particular to a two stroke cycle rotary engine of the Wankel type.
2. Discussion of the Technical Problems
Wankel type rotary internal combustion engines have "pistons" rotating within an epitrochoidal housing so that the tips of the rotating body, or piston, maintain contact with the housing and produce an ever changing shaped combustion chamber. Engines of this type have been invented since at least 1961. Engines of this type are known as Wankel Rotary Engines and it is generally accepted that such engines were invented by Felix Wankel. In fact, Felix Wankel described the geometry for such engines in U.S. Pat. No. 2,988,008 issued Jun. 13, 1961.
The Wankel engine provides spaces between the inner rotor and the outer housing or epitrochoid that define variable volumes which are used as compressor chambers. Such rotary engines have been adopted by a number of manufacturers and generally follow the geometric configuration as defined in the Wankel patent. The Wankel engine in widest use employs a three-faced rotating body or "rotor" having three tip seals. The rotor revolves about an eccentric with appropriate phasing gears so that the three tip seals move about the epitrochoid to create cavities of varying volume as the rotor rotates.
Felix Wankel further defined the rotary internal combustion engine in his co-issued U.S. Pat. No. 2,988,065 dated Jun. 13, 1961. The engine that is disclosed in that patent along with subsequent developments have shown that the rotor must complete the equivalent of a four stroke cycle in order to properly produce power. By having the spark plug mounted on one side of the epitrochoid housing defining the compression and power cycles, the opposite chamber can be utilized for exhaust and intake cycles. Multiple rotor engines were thereupon designed to take advantage of that basic four stroke cycle configuration.
Unfortunately in the standard four stroke cycle rotary internal combustion engine of the Wankel type, the area near the spark plug becomes quite heated, whereas the opposite side of the engine near the intake region is relatively cold. Accordingly, the standard Wankel type engine exhibits a heat imbalance. One way of appropriately cooling the heated portion of the engine is to design the external housing to have sufficient cooling fins and the like to offset the uneven cooling that is produced in the normal four stroke Wankel engine.
While prior art rotary internal combustion engines of the Wankel type are generally of the type having a fixed epitrochoidal cavity or housing with one or more rotating pistons known as rotors, it has been disclosed by Wankel and others that the rotor/crankshaft could be held stationary and the epitrochoidal housing could be rotated. While such an arrangement appears to be fine in theory, such engines have been somewhat difficult to design. Accordingly, one finds that the common rotary engine is of the type having a stationary housing.
If on the other hand, one were to rotate either the crankshaft or the housing and have the housing or the crankshaft operably attached to a compressor, a source of compressed air could be produced. Such compressed air could be introduced into the engine and serve as an intake charging means. The raised air pressure would also serve to force the exhaust gases out of the chamber if the intake and exhaust ports were properly designed. Additionally, such a source of compressed air, while providing a source of pressure in order to maintain the proper flow of gases in a two stroke cycle engine, could also provide some cooling bypass air if properly ducted.
The instant invention thus provides a two stroke Wankel type rotary engine having a source of compressed air. If a compressor were to be driven externally of the engine to provide the necessary pressure to operate the two stroke Wankel engine, then even the type of engine having a stationary epitrochoidal housing and moving crankshaft could be employed.
While few known examples of two stroke rotary engines have been discovered, U.S. Pat. No. 2,988,008 to Felix Wankel issued Jun. 13, 1961, and U.S. Pat. No. 2,988,065, also to Felix Wankel, issued Jun. 13, 1961, disclose the basic Wankel engine.
German patent No. 1,300,123 to Horst Mai issued Jul. 31, 1969 discloses a two stroke Wankel engine with poppet valves and intake and exhaust ports on the same side wall of the housing. Unfortunately, the Mai invention necessarily requires the poppet valves since the porting arrangement would not otherwise allow for sufficient scavenging and the Mai seal arrangement requires that the intake and exhaust ports are on the same side wall of the housing.
U.S. Pat. No. 3,967,594 to Campbell issued Jul. 6, 1976 discloses a particular three lobe, compression ignition (Diesel) engine with an elliptical piston and unique gearing and eccentric means supporting the piston within the casing. Unfortunately, the Campbell invention requires that the intake ports are spaced farther from the center of the casing than the exhaust ports and the Campbell invention necessitates that compression ignition and a stationary housing be used.
Very few devices in the known art relate to two stroke rotary engines and none known are directed to two stroke Wankel type rotary internal combustion engines with intake ports on one side wall and exhaust ports on the other side wall of the housing. Also no known devices relate to such engines providing a source of compressed air which is used as scavenging intake air as well as for cooling bypass air.
The instant invention is directed to all of these needs as well as to others as explained in the following summary.